Inorganic particulate materials may be added to polymers to improve their properties and/or to reduce cost by reducing the amount of polymer used in the composition. Diatomaceous earth is one example of an inorganic particulate material that may be added to polymers. Diatomaceous earth, also known as DE, diatomite and kieselgur, is a naturally occurring soft sedimentary rock. It is principally composed of the silica microfossils of aquatic unicellular algae known as diatoms. Diatomaceous earth typically has a chemical composition in the range of about 60 to 95% silica, 1 to 12% alumina and 0.5 to 8% iron oxide. It may also contain small amounts of other compounds such as calcium oxide, titanium dioxide, magnesium oxide, sodium oxide and potassium oxide. Diatomaceous earth has a highly porous structure, for example containing up to 80 to 90% voids, and consists of particles of a wide variety of shapes and sizes.
Diatomaceous earth demonstrates good sorption ability, chemical inertness and low density. It may be used as a filter-aid in the processing of liquid foodstuffs and chemical fluids, as a filler in plastics and paints, and as a raw material for the production of insulation bricks. The use of diatomaceous earth as a filler may affect properties such as colour, oil absorption, surface wetting and bonding, chemical resistance and mechanical properties (e.g. physical strength) of the materials in which they are used.
It may be desirable to provide at least an alternative inorganic particulate material (e.g. an alternative diatomaceous earth) suitable for use as a filler in various compositions, for example as a filler in polymer compositions. It may also be desirable to provide an improved inorganic particulate material (e.g. an improved diatomaceous earth) for use as a filler in various compositions, for example as a filler in polymer compositions. Since diatomaceous earth is often relatively cost-effective in comparison to other inorganic particulate fillers such as kaolin, calcium carbonate and silica, it may be desirable to provide an alternative and/or improved diatomaceous earth which could be used to partially or completely replace other fillers in a composition, for example in a polymer composition.